Vehicles having propulsion systems that combust fuel may travel though areas that reduce the flow or air or oxygen content in the air that negatively impact performance of the propulsion systems. These areas can be referred to as airflow restricting areas, and may result in less air being available for combustion by the propulsion systems. As a result, the power generated by the propulsion systems to propel the vehicles may be significantly decreased during travel in these areas. Examples of such fresh airflow restricting areas include tunnels and valleys.